e0204f8d46
Caching path info is generally useful. For instance, it speeds up "nix path-info -rS /run/current-system" (i.e. showing the closure sizes of all paths in the closure of the current system) from 5.6s to 0.15s. This also eliminates some APIs like Store::queryDeriver() and Store::queryReferences().
74 lines
1.2 KiB
C++
74 lines
1.2 KiB
C++
#pragma once
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#include <memory>
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#include <exception>
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#include <stdexcept>
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namespace nix {
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/* A simple non-nullable reference-counted pointer. Actually a wrapper
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around std::shared_ptr that prevents non-null constructions. */
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template<typename T>
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class ref
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{
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private:
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std::shared_ptr<T> p;
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public:
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ref<T>(const ref<T> & r)
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: p(r.p)
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{ }
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explicit ref<T>(const std::shared_ptr<T> & p)
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: p(p)
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{
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if (!p)
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throw std::invalid_argument("null pointer cast to ref");
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}
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T* operator ->() const
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{
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return &*p;
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}
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T& operator *() const
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{
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return *p;
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}
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operator std::shared_ptr<T> ()
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{
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return p;
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}
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template<typename T2>
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ref<T2> cast()
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{
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return ref<T2>(std::dynamic_pointer_cast<T2>(p));
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}
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template<typename T2>
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operator ref<T2> ()
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{
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return ref<T2>((std::shared_ptr<T2>) p);
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}
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private:
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template<typename T2, typename... Args>
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friend ref<T2>
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make_ref(Args&&... args);
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};
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template<typename T, typename... Args>
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inline ref<T>
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make_ref(Args&&... args)
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{
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auto p = std::make_shared<T>(std::forward<Args>(args)...);
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return ref<T>(p);
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}
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}
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